Hydraulic lifting devices for tractors



Sept. 10, 1963 1.. PERAS 3,103,

HYDRAULIC LIFTING DEVICES FOR TRACTORS Filed Dec. 25. 1960 United States Patent- 3,103,147 HYDRAULIC LIFTING DEVICES FOR TRACTORS Lucien Pras, Billancourt, France, assignor to Regie Nationale des Usines Renault, Billancourt, France Filed Dec. 23, 1960, Ser. No. 78,134 Claims priority, application France Dec. 23, 1959 4 Claims. (Cl. 91-48) The present invention relates to hydraulic lifting for tractors in general and has specific reference to an improved device of this character which is intended more particularly for equipping tractors having a so-called universal coupling gear or a well-known three-point coupling gear.

It is the primary object of this invention to provide means adapted to maintain at a preselected constant level the points at which the farming implements, machine or equipment are attached to the links of the coupling gear, irrespective of the movements imparted by the ground unevennesses to the coupled equipment.

According to another feature characterizing this invention the device comprises a control hand lever of which each position corresponds to a given position of the points of attachment of the coupled machine.

With these two features a desired constant working depth can easily be obtained when changing from one working place to another.

With the device of this invention it is also possible to transfer to the rear or drive axle of the tractor one fraction of the weight of the equipment or machine coupled thereto without lifting the latter to this end, so that in difiicult cases the wheel adherence of the tractor and therefore its tnactive power maybe increased considerably. The load transfer control hand-lever is mounted on the sector receiving the lifting control hand lever; this load transfer control lever responsive to the drivers hand acts upon a piston adjusting the section of the passage leading to the chamber of the leakage valve, the latter being kept open by the entire oil output delivered by the pump.

Finally, the arrangement constituting the subject matter of this invention permits'of supplying in a simple manner oil under pressure to one or more auxiliary lifting cylinders.

The single FIGURE of the attached drawing illustrates diagrammatically by way of example a device constructed according to this invention, and shows in axial section the essential component elements of this device.

Referring to the drawing, the feed pipe or conduit 2 is connected to the oil pump (not shown) and leads to a chamber 29 communicating through an orifice 30 with the chamber 31 receiving the leakage valve 17; this valve 17 is an integral part of piston 16 provided with a piston rod 16 and the valve 17 and the piston 16 thus define a differential valve. This piston 16 is slidably mounted in a cylinder 16 communicating at one end with the discharge duct 32 through which the oil may flow directly into the oil sump =1 and at the other end with the chamber 35. This chamber 35 opens into the cylinder 34 receiving the slide valve .18 having two working portions and 10 The slide valve It) is connected through a linkage system 11 to the arm 9 controlling the lifting movement of the equipment coupled with the tractor.

This system is controlled by the lever or handle 12 displaceable along a sector.

The cylinder 34 communicates with the duct 35 connected to the oil feed pipe 2 and leading into the cylinder '34 between the two working portions 10 and' 10 of slide 'valve 110. This cylinder 34 is formed on its end adjacent 3,103,147. Patented Sept. 10, 1963 ice will be noted that a difference of about .004" to .006 is provided between the width of groove 36 and that of the aforesaid working portion 10 of the slide valve. The discharge or lowering valve designated by the reference numeral 18 is normally seated by a spring 18 this valve controls the communication between the discharge conduit or duct 19 leading to the cylinder 5 in which the piston 6 controlling the lifting arm 9 is slidably mounted, and the discharge duct or orifice 38 leading to the oil sump. The inclined or bevel edge 39 of the other working portion 10 of slide valve 10 controls the discharge or lowering valve 18 through its stem 20, the valve '18 and stem 20 forming a unitary member in this structure.

Branched oil the duct 19 is a pipe 44 controlled by a spring-loaded non-return valve 23; this pipe 44 leads to the oil feed pipe 2. A needle or variable-orifice valve 21 is mounted in the aforesaid duct 19 between the lowering or discharge valve 18 and the non-return valve 23. The

three-way cock 27 controls the communication between the duct 19 and the pipe 23 leading to auxiliary control cylinders (not shown) and supplying oil under pressure thereto.

The operation of this device is as follows:

When, as shown in the drawing, the arm 9 occupies a given position dependent upon the position of the lever 12, as will appear from the following, the leakage valve 17 is maintained in its open position by the whole of the oil output delivered by the pump through the feed pipe 2. The 'oil flows from the chamber 29 through the orifice 30 into chamber 31 and its pressure moves the piston 16 to the left (as seen in the drawing), thus unseating the valve 17 and opening the communication from the cylinder 31 to the discharge duct 32 leading to the oil sump. The chamber 29, the orifice 30, the chamber 31 and the duct 32 thus define a leakage conduit for said feed conduit 2.

To obtain, for example, the raising of arm 9, the lever 12 is displaced in the direction of the arrow F. The arm 9 being motionless, the lever 12 actuates the articulated system 11 in the direction of displacing the valve 10 towards the left as shown in the drawing and the part 10' of this valve begins to close the groove 36 on the side leading through duct 37 to the oil sump, whereafter this groove 36 is re-opened but on the feed side through the control conduit or duct 35 between the two working portions 10 and =10 The cylinder 35 is then placed under pressure and. the pressure acting on the piston 16 effects the closing of the valve 17.

The pressure in cylinder 31 communicating directly with the oil sump will 'always be lower than that existing in the duct 35 and therefore it will not interfere with the displacement of piston 16; under these conditions, any risk of balancing the pressures is precluded.

On the other hand, when the valve 17 begins to close, the lifting pressure builds up throughout the circuit and the valve .17 is seated by a force equal to this pressure multiplied by the cross-sectional area of the valve seat (the piston 16 being put in equilibriumby the same pressure on either side). Then the oil under pressure from pipe 2 will flow through duct 44, unseat the non-return valve 23 and then flow through duct 19 into the cylinder 5 to move the piston 6 to the right, which effects the raising of the lifting arm 9. Under the effect of the raising of arm 9, the lever 12 then remaining stationary, the articulated system 11 is actuated in the direction to move the valve 10 to the right as seen. in the drawing, viz towards its neutral initial position.

Upon completion of the lifting movement, when the slide valve 10 responsive to the linkage system 11 has closed the orifice through which chamber 35 was fed with oil under pressure andhas subsequently opened the discharge passage from this chamber, the pressure prevailing in chamber 31 moves the piston 16 to force the oil out from chamber 35.

As long as valve 17 is not sufliciently open, a pressure will prevail at 31 which continues. to push the piston 16 to the diiferent possible positions of the lever 12 predetermined positions of the arm 9.

' To obtain a lowering of the arm 9, the lever 12 is displaced in the direction opposite the arrow F, and the articulated system '11 is then actuated to displace the valve 10 to the right as seen in the drawing. The beveled edge 39 of the valve -10 thus actuates the stem 20 to open the valve 18. The oil from cylinder then returns to the sump '-1 through conduit 19, the valve 18 and the conduit 38, and passing through the needle valve 21 which can be regulated to obtain the desired speed of descent. When the-arm 9 is lowered, the lever 12 remains stationary and the valve is then moved towards the left into its neutral position :by means of the articulated system '11.

In the arrangement constituting the subject-matter of this invention the supply of oil for lifting purposes takes place only through the pipe 44 and valve 23. As the por tion receiving the push rod or stem controlling the lowering valve 18 is never under pressure, any risk of leakage is definitely precluded.

It is an essential feature of the invention to provide an improved load transfer device wherein a piston or throttling element valve 40 slidably mounted in a chamber 29 has its rod connected through a link and-rod system 41 to a shaft 42 carrying the control lever 43 displ-alceable on the same sector as the other control lever 1'2. The chamber 29 and piston 40 thus define a throttling valve.

The load transfer control member is thus mounted on the same sector as the lifting control lever 12.

' By means of a piston 40 the transfer control is rendered sensitive so that the more the toil discharge (orifice 36} is throttled by the piston 40, the higher the oil pressure in the circuit which acts upon the piston 6. This pressure is alsov exerted on the piston 4t} and is responsive to the control hand lever 43. The feeling of resistance (proportional to the weight of the equipment which is transferred to the tractor) increases until a leakage occurs through the valve 18. In effect, when the pressure in the jack increases to the point of displacing'the piston 6 towards the right, viz the raising of arm 9, this last-named action actuates the articulated system .11 in the direction of displacing the valve 10 towards the right in the drawing, viz in the direction of opening the valve 18. Then .a selfbalancing condition is obtained. The pressure does not increase anymore and corresponds to the weight of the equipment. The total weight of the equipment is thus transferred to the rear or drive wheels of the tractor without the arm 9, and thus the equipment, being raised to any measurable extent.

When the load transfer is thus self-balanced, the oil is A discharged directly to the oil sump through duct 38.

I claim:

1. A device adapted for use with an agricultural tractor having implements attached thereto for the hydraulic lifting of the implements carried by said agricultural hactor comprising, in combination, a simple-effect fluid jack having a cylinder and a piston movable therein, a lifting arm connected to said piston of said jack and adapted to elfect the desired raising and lowering of said implements, a fluid feed conduit in a circuit connected to the cylinder of said jack, said circuit including a nonreturn valve, a leakage conduit connected to said feed conduit upstream of said valve, a discharge conduit connected to the feed conduit between the jack and the nonreturn valve, and having a discharge orifice, a discharge valve positioned to control said orifice, a differential valve positioned to control the flow of fluid from said 4 leakage conduit, a slide valve positioned to control the differential valve and the discharge valve, a control conduit connected to the feed conduit upstream of the nonreturn valve and communicating with the slide valve, means defining a cylinder in which said differential valve is slidably disposed, said last-named cylinder comprising two chambers separated from each other by said'differential valve, one of said chambers forming part of said leakage conduit and said leakage conduit also including a leakage orifice in communication with said one of said chambers and disposed to be closed byv said differential valve, an auxiliary conduit communicating with the other of said chambers, and said slide valve controlling communication between said auxiliary conduit and the atmosphere and between said auxiliary conduit and said control conduit, said slide valve also being disposed in position to engage said discharge valve when said auxiliary conduit is in communication with the atmosphere, a manual control lever, a linkage system interconnecting said manual control lever, said slide valve, and said lifting arm to provide a follow-up control, and a throttling valve disposed in said leakage conduit, said throt- .tling valve being manually controllable.

2. A device adapted for use with an agricultural trac tor having implements attached thereto for the hydraulic lifting of the implements carried by said agricultural tractor comprising, in combination, a simple-effect fluid jack having a cylinder and a piston movable therein, a lifting arm connected to said piston of said jack and adapted to effect the desired raising and lowering of said implements, a fluid feed conduit in a circuit connected to the cylinder of said jack, said circuit including a non-return valve, a leakage conduit connected to said feed conduit upstream of said valve, a discharge conduit connected to the feed conduit between the jack and the non-return valve, and having a discharge orifice, a discharge valve positioned to control said orifice, a differential valve positioned to control the flow of fluid from said leakage conduit, a slide valve positioned to control the differential valve and the discharge valve, a control conduit connected to the feed conduit upstream of the non-return valve and communicating with the slide valve, means defining a cylinder in which said differential valve is slidably disposed, said last-named cylinder comprising two chambers separated from each other by said differential valve, one of said chambers forming part of said leakage conduit and said leakage conduit also including a leakage orifice in communication with said one of said chambers and disposed to be closed by said difierential valve, an "auxiliary conduit communicating with the other of said chambers, and said slide valve controlling communication between said auxiliary conduit and the atmosphere and between said auxiliary conduit and said control conduit, said slide valve also being disposed in position to engage said discharge valve when said auxiliary conduit is in communication with the atmosphere, a manual control lever, a linkage system interconnecting said manual control lever, said slide valve, and said lifting arm to provide a follow-up control, and a throttling valve disposed in said leakage conduit, said throttling valve being manually controllable, and said throttling valve comprising a chamber forming part of said leakage. conduit, said last-named chamber having .a passage forming part of said leakage conduit for the flow of the leakage fluid therethrough, and a throttling element slidable in said last-named chamber, said throttling element being movable in a direction opposite to that in which the fluid pressure upstream of said passage acts upon it.

3. A device adapted for use with an agricultural tractor having implements attached thereto for the hydraulic lifting of the implements carried by said agricultural tractor comprising, in combination, a simple-effect fluid jack having a cylinder and a piston movable therein, a lifting arm connected to said piston of said jack and adapted to effect the desired raising and lowering of said implements, a fluid feed conduitin a circuit connected to the cylinder of said jack, said circuit including a nonreturn valve, a leakage conduit connected to said feed conduit upstream of said valve, a discharge conduit connected to the feed conduit between the jack and the nonreturn valve, and having a discharge orifice, a discharge valve positioned to control said orifice, a diflerential valve positioned to control the flow of fluid from said leakage conduit, a slide valve positioned to control the differential valve and the discharge valve, a control conduit connected to the feed conduit upstream of the nonreturn valve and communicating with the slide valve, means defining a cylinder in which said difierential valve is slidably disposed, said last-named cylinder comprising two chambers separated from each other by said differen tial valve, one of said chambers forming part of said leakage conduit and said leakage conduit also including a leakage orifice in communication with said one of said chambers and disposed to be closed by said differential valve, an auxiliary conduit communicating with the other of said chambers, and said slide valve controlling communication between said auxiliary conduit and the atmosphere and between said auxiliary conduit and said control conduit, said slide valve also being disposed in position to engage said discharge valve when said auxiliary conduit is in communication with the atmosphere, a manual control lever, a linkage system interconnecting said manual control lever, said slide valve, and said lifting arm to provide a follow-up control, and a throttling valve disposed in said leakage conduit, said throttling valve being manually controllable, and a variable orifice valve disposed in said discharge conduit.

4. A device adapted for use with an agricultural tractor having implements attached thereto for the hydraulic lifting of the implements carried by said agricultural tractor comprising, in combination, a simple-efiect fluid jack having a cylinder and a piston movable therein, a lifting arm connected to said piston of said jack and adapted to effect the desired raising and lowering of said implements, .a fiuid feed conduit in a circuit connected to the cylinder of said jack, said circuit including a non-return valve, a leakage conduit connected to said feed conduit upstream of said valve, a discharge conduit connected to the feed conduit between the jack and the non-return valve, and having a discharge orifice, a discharge valve positioned to control said orifice, a differential valve positioned to control the flow of fluid from said leakage conduit, a slide valve positioned to control the differential valve and the discharge valve, a control conduit connected to the feed conduit upstream of the non-return valve and communicating with the slide valve, means defining a cylinder in which said differential valve is slidably disposed, said last-named cylinder comprising two chambers separated from each other by said differential valve, one of said chambers forming part of said leakage conduit and said leakage conduit including a leakage orifice in communication with said one of said chambers and disposed to be closed by said differential valve, an auxiliary conduit communicating with the other of said chambers, and said slide valve controlling communication betweensaid auxiliary conduit and the atmosphere and between said auxiliary conduit and said control conduit, said slide valve also being disposed in position to engage said discharge valve when said auxiliary conduit is in communication with the atmosphere, a manual control lever, a linkage system interconnecting said manual control lever, said slide valve, and said lifting arm to provide a follow-up control, and a throttling valve disposed in said leakage conduit, said throttling valve being manually controllable, and said throttling valve comprising a chamber forming part of said leakage conduit, said last named chamber having a passage forming part of said leakage conduit for the flow of the leakage fluid therethrough, and a throttling element slidable in said last-named chamber, said throttling element being movable in a direction opposite to that in which the fluid pressure upstream of said passage acts upon it, and a variable orifice valve disposed in said discharge conduit.

References Cited in the file of this patent UNITED STATES PATENTS 1,479,386 Hynes et al. Ian. 1, 1924 2,477,710 Worstell Aug. 2, 1949 2,821,173 Adsit Ian. 28, 1958 2,847,030 McRae Aug. 12, 1958 2,964,908 Pomper et al. Dec. 20, 1960 

1. A DEVICE ADAPTED FOR USE WITH AN AGRICULTURAL TRACTOR HAVING IMPLEMENTS ATTACHED THERETO FOR THE HYDRAULIC LIFTING OF THE IMPLEMENTS CARRIED BY SAID AGRICULTURAL TRACTOR COMPRISING, IN COMBINATION, A SIMPLE-EFFECT FLUID JACK HAVING A CYLINDER AND A PISTON MOVABLE THEREIN, A LIFTING ARM CONNECTED TO SAID PISTON OF SAID JACK AND ADAPTED TO EFFECT THE DESIRED RAISING AND LOWERING OF SAID IMPLEMENTS, A FLUID FEED CONDUIT IN A CIRCUIT CONNECTED TO THE CYLINDER OF SAID JACK, SAID CIRCUIT INCLUDING A NONRETURN VALVE, A LEAKAGE CONDUIT CONNECTED TO SAID FEED CONDUIT UPSTREAM OF SAID VALVE, A DISCHARGE CONDUIT CONNECTED TO THE FEED CONDUIT BETWEEN THE JACK AND THE NONRETURN VALVE, AND HAVING A DISCHARGE ORIFICE, A DISCHARGE VALVE POSITIONED TO CONTROL SAID ORIFICE, A DIFFERENTIAL VALVE POSITIONED TO CONTROL THE FLOW OF FLUID FROM SAID LEAKAGE CONDUIT, A SLIDE VALVE POSITIONED TO CONTROL THE DIFFERENTIAL VALVE AND THE DISCHARGE VALVE, A CONTROL CONDUIT CONNECTED TO THE FEED CONDUIT UPSTREAM OF THE NONRETURN VALVE AND COMMUNICATING WITH THE SLIDE VALVE, MEANS DEFINING A CYLINDER IN WHICH SAID DIFFERENTIAL VALVE IS SLIDABLY DISPOSED, SAID LAST-NAMED CYLINDER COMPRISING TWO CHAMBERS SEPARATED FROM EACH OTHER BY SAID DIFFERENTIAL VALVE, ONE OF SAID CHAMBERS FORMING PART OF SAID LEAKAGE CONDUIT AND SAID LEAKAGE CONDUIT ALSO INCLUDING A LEAKAGE ORIFICE IN COMMUNICATION WITH SAID ONE OF SAID CHAMBERS AND DISPOSED TO BE CLOSED BY SAID DIFFERENTIAL VALVE, AN AUXILIARY CONDUIT COMMUNICATING WITH THE OTHER OF SAID CHAMBERS, AND SAID SLIDE VALVE CONTROLLING COMMUNICATION BETWEEN SAID AUXILIARY CONDUIT AND THE ATMOSPHERE AND BETWEEN SAID AUXILIARY CONDUIT AND SAID CONTROL CONDUIT, SAID SLIDE VALVE ALSO BEING DISPOSED IN POSITION TO ENGAGE SAID DISCHARGE VALVE WHEN SAID AUXILIARY CONDUIT IS IN COMMUNICATION WITH THE ATMOSPHERE, A MANUAL CONTROL LEVER, A LINKAGE SYSTEM INTERCONNECTING SAID MANUAL CONTROL LEVER, SAID SLIDE VALVE, AND SAID LIFTING ARM TO PROVIDE A FOLLOW-UP CONTROL, AND A THROTTLING VALVE DISPOSED IN SAID LEAKAGE CONDUIT, SAID THROTTLING VALVE BEING MANUALLY CONTROLLABLE. 